Melting pistons.

Accelerator

Accelerator

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McRat said:
Both LB7/LLY(same) design pistons melt, as do the LBZ/LMM's(same). Cracking is the difference. LBZ/LMM are more prone to cracking. Seems there is a quality control issue with some of them. My best guess is that they have pressed in wristpin bushings. Press fitting parts into cast aluminum is always risky. If the process isn't perfect, the aluminum cracks, either right away, or over time. When I ran LBZ pistons in Casper, they didn't crack. They melted first. The only time I had a piston start to crack, was an LLY slug, but it was already destroyed by melting first.
Click to expand...

very interesting analisis on the pressed bushings affecting structural integrity
 
Accelerator

Accelerator

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McRat said:
Stock LB7's are .0065" x 7 IIRC. So .011"? Best described as garden hose nozzles. :eek:

About 300%?
Click to expand...

that cleared up my confusion. thanks

looks like stock LB7's are huge!! 45LPM...which adds up to his sig saying 80% over, that is 81 LPM..very close.
 
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Accelerator

Accelerator

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Johnboy, have you found that tuning and running a injector that big changes the way it runs, and or affects the reliabilty?
 
Accelerator

Accelerator

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Lets talk diesel fuels related to tuning.

Higher cetain makes the fuel ignite faster

Higher BTU's can make for a more powerfull explosion

is it possible that our fuel's are limiting our tuning ability AND our reliability???
 
Trippin

Trippin

SoCal Diesel
Aug 10, 2006
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Stock LB7 injectors flow 13% more than stock LBZ when rated at the same pressure and pulse width.
 
JOHNBOY

JOHNBOY

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Aug 30, 2006
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Accelerator said:
Johnboy, have you found that tuning and running a injector that big changes the way it runs, and or affects the reliabilty?
Click to expand...


Yes. Even the Smaller hones change the way it acts and reacts to timing and pressure. Can be very sensitive. The less commanded pressure you run the more forgiving things are. The more pressure the bigger the difference. Bigger injectors allow you to get the fuel in faster. Which means less overall pulse. The by products of that are you need less timing and you dont spray after TDC as much. comparing the tune now timing ad pulse wise to say my old stock injecors stuff shows big differences. It runs way smoother in the upper rpms. I cant speak about really speak about durabilty yet. It is a track truck so hours are very low. But all signs look good. I have had the heads off a couple times to fix sticking valves and the pistons looked dandy.:coolspot:
 
JOHNBOY

JOHNBOY

< Rocking the Big Single!
Aug 30, 2006
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Accelerator said:
Lets talk diesel fuels related to tuning.

Higher cetain makes the fuel ignite faster

Higher BTU's can make for a more powerfull explosion

is it possible that our fuel's are limiting our tuning ability AND our reliability???
Click to expand...

http://www.syndiesel.com/index.html

60 Cetane and it is thinner than regular pump diesel so it should flow better. I know no one that runs it but it sound good.
 
Accelerator

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JOHNBOY said:
http://www.syndiesel.com/index.html

60 Cetane and it is thinner than regular pump diesel so it should flow better. I know no one that runs it but it sound good.
Click to expand...

John robinson has a racing diesel in the works that he has been working on with torco fuels. his testing has netted 35HP everytime with just a change in fuel, same testing......this sounds good to.

the syndiesel i have not used or heard of anyone useing, but it does sound promising.
 
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Accelerator

Accelerator

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JOHNBOY said:
Yes. Even the Smaller hones change the way it acts and reacts to timing and pressure. Can be very sensitive. The less commanded pressure you run the more forgiving things are. The more pressure the bigger the difference. Bigger injectors allow you to get the fuel in faster. Which means less overall pulse. The by products of that are you need less timing and you dont spray after TDC as much. comparing the tune now timing ad pulse wise to say my old stock injecors stuff shows big differences. It runs way smoother in the upper rpms. I cant speak about really speak about durabilty yet. It is a track truck so hours are very low. But all signs look good. I have had the heads off a couple times to fix sticking valves and the pistons looked dandy.:coolspot:
Click to expand...

valves sticking due to high EGT? or lack of lube?
 
Accelerator

Accelerator

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JOHNBOY said:
Do to me learning how to build one of these engines. I did not have enough clearence in the guides and I ran valve seals.:banghead: No valve seals and more clearence fixed it.
Click to expand...

Yes allowing engine oil in the valve guide area during opperation, very wise....

Curtis had to pound that in my head before i grasped it too...:D
 
TheBac

TheBac

Why do I keep doing this?
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Apr 19, 2008
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Help....2 hrs reading....information overload....head going to explode....help


Excellent thread. Exceptional amount of information. Wish I understood half of it.
 
SmokeShow

SmokeShow

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Nov 30, 2006
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Burp... this third chapter has been a dandy!


This % over thing... that's generally stated as physical size % increase rather than flow increase %, right?
 
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